O'Reilly logo

Cisco ASA and PIX Firewall Handbook by Dave Hucaby

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

3-2. Configuring Routing

A firewall is a Layer 3 device, even though it inspects packets at many layers. Packets are forwarded based on their Layer 3 destination IP addresses, so the firewall must know how to reach the various destination IP networks. (This is true unless a firewall is configured for transparent firewall mode, where it operates only on Layer 2 information.)

A firewall knows about the subnets directly connected to each of its interfaces. These are shown as routes with a CONNECT (PIX 6.3) or directly connected (PIX 7.x) identifier in output from the show route command.

To exchange packets with subnets not directly connected, a firewall needs additional routing information from one of the following sources:

  • Static routes (manually ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required